Congenital Cornification Disorder (ILVEN) – Chihuahua

Congenital cornification disorder affects how the outer layer of the skin forms and sheds. There are two distinct mutations in Chihuahuas associated with congenital cornification disorder resembling Inflammatory Linear Verrucous Epidermal Nevus (ILVEN). These X-linked incomplete dominant mutations both affect the NAD(P) dependent steroid dehydrogenase-like (NSDHL) gene which encodes an enzyme that plays a critical role in cholesterol biosynthesis, which is essential for normal cell membrane structure, signalling, and skin barrier function.
Dogs affected by this disorder typically present with linear skin lesions. The lesions appear as thickened, verrucous (wart-like), and scaly plaques, often distributed in a unilateral or segmental fashion. These skin changes are persistent, non-healing, and may be painful or itchy. Importantly, ILVEN in dogs is similar to the human CHILD syndrome, though it is limited to the skin, with no systemic involvement. ILVEN is homozygous lethal mutation, therefore only female dogs will be affected. Any male embryos carrying the mutation will spontaneously abort.